Method for transmitting data streams, and warm start sequence for S(H)DSL transmission/reception devices

ABSTRACT

The invention relates to a method for transmitting data streams where transmission/reception devices (LTU, NTU) deactivated to a standby state are activated by performing a warm start sequence, with transmission line parameters being determined (S 103 ) using an exchange-end transmission/reception device (LTU) following provision of a subscriber-end transmitted signal, transmission line parameters being determined (S 104 ) using a subscriber-end transmission/reception device (NTU) following provision of an exchange-end transmitted signal, echo cancelation being realigned (S 105 ) using a subscriber-end transmission/reception device (NTU) following provision of a subscriber-end transmitted signal, and/or echo cancelation being realigned (S 106 ) using an exchange-end transmission/reception device (LTU) following provision of an exchange-end transmitted signal.

[0001] The present invention relates to a method and to an apparatus fortransmitting data streams, and relates in particular to a method fortransmitting data streams where transmission/reception devicesdeactivated to a standby state are activated by performing a warm startsequence.

[0002] With transmission methods using copper lines, there is theproblem of transferring exchange-end transmission/reception devices andsubscriber-end transmission/reception devices connected via at least onedata transmission path from a deactivated state or from a standby stateto an activated state, this operation being referred to below as a “warmstart”.

[0003] XDSL technologies involve various types of use/carrier methodsfor line-conducted data stream transmission from an exchange to asubscriber end.

[0004] By way of example, the following DSL (DSL=Digital SubscriberLine) methods are used:

[0005] (i) ADSL: asymmetric DSL,

[0006] (ii) VDSL: Very High Data Rate DSL,

[0007] (iii) SDSL: Symmetrical Single Pair DSL (DSL with a symmetricalsingle pair line), and

[0008] (iv) S(H)DSL: (SDSL at a high data rate).

[0009] These transmission methods using the at least one datatransmission path are based on exchange-end transmission/receptiondevices and subscriber-end transmission/reception devices, the problembeing that both transmission/reception devices need to be transferred toan energy saving mode, or need to be deactivated, for energy savingreasons.

[0010] To change from an energy saving mode or a standby mode to anoperating mode, the deactivated transmission/reception devices need tobe reactivated using a warm start sequence.

[0011] In this context, it can be assumed that a first warm startsequence has been preceded by a “cold start”, where data transmissionhas been activated on a line.

[0012] The exchange-end transmission/reception devices and thesubscriber-end transmission/reception devices adapt themselves in thiscase to the parameters or properties of the line in the datatransmission path.

[0013] Disadvantageously, this operation typically takes at least 30seconds, which means that a warm start, which comprises a warm startsequence and requires much shorter time periods for activation, isabsolutely essential. In this context, all subsequent activationoperations require that knowledge of the properties of the line in thedata transmission path be put into practice in a fraction of theaforementioned time (30 seconds).

[0014] All of these activation operations are referred to as “warmstarts”. Internationally standardized warm start sequences exist forISDN-U interfaces, for example, as described in the literaturereference:

[0015] “ETSI TS 102 080, Integrated Services Digital Network (ISDN)basic rate access, Third Edition, November 1998”and in the literaturereference:

[0016] “ANSI T1.601-1988, Integrated Services Digital Network (ISDN),ANSI, September 1988”.

[0017] For xDSL, particularly for S(H)DSL methods, various methods areknown which all have serious drawbacks for existingtransmission/reception devices. Such methods are described in theliterature references

[0018] “Infineon, “SDSL Warm Start Capability”, ETSI-Meeting TM6Amsterdam, December 1999, 994t51a0”;

[0019] “Adtran, “Warm Start Considerations”, ETSI-Meeting TM6 Amsterdam,December 1999, 994t59a0”; “Infineon, Adtran, “SDSL Warm Start”,Helsinki, May 2000, 002t25a1”;

[0020] “Infineon “Warmstart Wake-up tones” ETSI-Meeting TM6 ViennaSeptember 2000, 003t42a0”;

[0021] “Conexant Systems “Warm start wake up signals” ETSI-Meeting TM6Monterey, November 2000, 00t24a0”;

[0022] “Conexant Systems “M-Sequence based line probe signals for bothkeep-alive and warmstart wake-up signals” ETSI-Meeting TM6 SophiaAntipolis, February 2001, 011t25a0”; and

[0023] “Infineon, “warmstart-Sequence”, ETSI-Meeting TM6 Ghent, May2001”; “Infineon “Warmstart wake-up tones”, Ghent, May 2001”.

[0024]FIG. 3 shows a flowchart in block form to illustrate a method fortransmitting data streams in accordance with the prior art. Following astart step S100, subscriber-end activation is effected in asubscriber-end activation step S101. The subscriber-end activationprovokes exchange-end activation, which is performed in an exchange-endactivation step. This is conventionally followed by subscriber-endsynchronization (step S107) and finally exchange-end synchronization(step S108): after steps S101-S108, a data stream can be transmitted ina data stream transmission step S111. Following data streamtransmission, the procedure is stopped (step S112).

[0025] A main drawback of conventional methods for transmitting datastreams where transmission/reception devices can be deactivated to astandby state is that, before synchronization or before a specific warmstart, a known far end signal needs to be provided in order to detect achange in the far end signal as a consequence of a change in propertiesof a line in the at least one data transmission path since activationlast occurred.

[0026] By way of example, interference such as temperature fluctuationsor changes in air humidity has a disadvantageous effect on lineproperties and can alter the line properties in an unforeseeable manner.

[0027] Another drawback of known methods is that transmission/receptiondevices are available which require a time period without a far endsignal before synchronization, in order to adapt themselves to a changein an echo in their own transmitted signal, which is also caused, interalia, by a change in line properties in the at least one datatransmission path.

[0028] Disadvantageously, a fixed warm start sequence in theexchange-end transmission/reception devices and in the subscriber-endtransmission/reception devices would mean a high level of complexity andwould lengthen a warm start sequence unnecessarily, resulting not onlyin an increase in costs but also in a reduction in the specificadvantages of a warm start.

[0029] It is therefore an object of the present invention to provide amethod for transmitting data streams where transmission/receptiondevices deactivated to a standby state are activated by performing awarm start sequence which does not require a fixed procedure and/ormakes no specific demands on the individual (exchange-end and/orsubscriber-end) transmission/reception devices and thus avoids thedrawbacks of methods based on the prior art.

[0030] The invention achieves this object by means of the methodspecified in patent claims 1, 6, 7, 8 and 9.

[0031] Further refinements of the invention can be found in thesubclaims.

[0032] A fundamental concept of the invention is that of prescribablyinserting at least one additional segment into a warm start sequencebefore synchronization is performed.

[0033] The invention provides four additional segments which can beinserted into a warm start sequence individually or in any combination,this being arranged either during a cold start activation operation orduring the activation (cold start or warm start) at a respectiveprevious time.

[0034] Specifically, these are

[0035] (i) an exchange-end transmission line determination step,

[0036] (ii) a subscriber-end transmission line determination step,

[0037] (iii) an exchange-end realignment step; and

[0038] (iv) a subscriber-end realignment step.

[0039] The aforementioned name “realignment step” relates to echocancelation.

[0040] It is thus a primary advantage of the present invention that anextremely flexible warm start sequence can be provided.

[0041] Before a warm start sequence, a successful cold start has bydefinition taken place, the cold start involving each end (exchange endand/or subscriber end) notifying the respective other end of thetransmission of specific signals.

[0042] The inventive method for transmitting data streams wheretransmission/reception devices deactivated to a standby state areactivated by performing a warm start sequence basically has thefollowing steps:

[0043] a) transmission line parameters are determined using anexchange-end transmission/reception device following provision of asubscriber-end transmitted signal;

[0044] b) transmission line parameters are determined using asubscriber-end transmission/reception device following provision of anexchange-end transmitted signal;

[0045] c) echo cancelation is realigned using a subscriber-endtransmission/reception device following provision of a subscriber-end,i.e. its own, transmitted signal; and

[0046] d) echo cancelation is realigned using an exchange-endtransmission/reception device following provision of an exchange-end,i.e. its own, transmitted signal.

[0047] The subclaims contain advantageous developments and improvementsof the respective subject matter of the invention.

[0048] In accordance with one preferred development of the presentinvention, S(H)DSL activation frames respectively contain two bits perdata transmission direction, said bits determining which of the steps a)to d) listed above are performed.

[0049] In accordance with another preferred development of the presentinvention, time periods for signals used to realign echo cancelation aretransmitted.

[0050] In accordance with yet another preferred development of thepresent invention, waiting time periods can be prescribed on a variablebasis between successive sequences.

[0051] Exemplary embodiments of the invention are illustrated in thedrawings and are explained in more detail in the description below.

[0052] In the drawings:

[0053]FIG. 1 shows a graphic of a warm start sequence with fouradditional segments in accordance with an exemplary embodiment of thepresent invention;

[0054]FIG. 2 shows a flowchart for a method for transmitting datastreams where transmission/reception devices deactivated to a standbystate are activated by performing a warm start sequence in accordancewith an exemplary embodiment of the present invention; and

[0055]FIG. 3 shows a flowchart for transmission of data streams in asequence based on the prior art.

[0056]FIG. 1 shows a warm start sequence, with a distinction being drawnbetween steps performed in an exchange-end transmission/reception deviceLTU and steps performed in a subscriber-end transmission/receptiondevice NTU.

[0057] Normally, a warm start sequence is started from the subscriberend by virtue of a “wake-up signal” being transmitted, whereupon aresponse is sent by the exchange end using the exchange-endtransmission/reception device. It will be pointed out that it islikewise possible for the exchange-end transmission/reception device LTUto provide a “wake-up signal”, in which case there is no waiting herefor a response from the subscriber-end transmission/reception deviceNTU.

[0058] The individual steps of the warm start sequence shown in FIG. 1are plotted along a time axis (Time), where individual time-periodintervals indicated by double arrows are not necessarily identical, butrather can be of variable length.

[0059] In a subscriber-end activation step S101, a subscriber-end“wake-up signal” is transmitted during an activation time t_(WUN)(WUN=Wake-up from NTU, from the subscriber-end transmission/receptiondevice). In the exchange-end activation step S102, the exchange-endtransmission/reception device LTU reacts to the signal W_(WUN) with asignal W_(WUL). The next seven time steps are performed on the basis ofan exemplary embodiment of the present invention, with a time t_(WS)denoting a prescribable waiting time.

[0060] It will be pointed out that, although the waiting times are shownin FIG. 1 as time periods of equal length, the waiting times can assumedifferent time periods.

[0061] In accordance with the invention, it is then possible toprescribe whether none or at least one of the steps S103-S106 isperformed.

[0062] In step S103, subscriber-end transmission line determination isperformed, with a signal W_(LPN) being transmitted. In the same way,exchange-end transmission line determination takes place in a step S104,with a signal W_(LPL) being transmitted. The two transmission linedetermination steps are used for effectively determining the propertiesof a specific transmission line in the at least one data transmissionpath for a warm start. It will be pointed out that steps S103-S106 canbe performed in any order in accordance with the invention.

[0063] On the basis of the invention, which of steps S103-S106 isperformed and in what order the steps to be performed are performed aredetermined most simply by two bits per data transmission direction.

[0064] In this context, the invention involves the use of the S(H)DSLactivation frame, which contains up to 67 unused bits to be used asfollows for an exemplary embodiment of the invention:

[0065] 1st bit: request for a signal for transmission linedetermination,

[0066] 2nd bit: request for a break in transmission in the remotestation for the purpose of realigning own echo cancelation;

[0067] 3rd to 67th bits: not yet used.

[0068] It will be pointed out that any other order and arrangement ofthe bits in the 67-bit-long block of unused bits comes within the scopeof the present invention.

[0069] As FIG. 1 shows, performance of steps S103 and S104, for example,is followed by a subscriber-end realignment step S105, where an echocancelation signal W_(ECN) is transmitted during a time period t_(ECN).

[0070] This echo cancelation signal is used to perform subscriber-endrealignment. A subsequent exchange-end realignment step performs a stepwhich is equivalent to step S105 from the exchange end, i.e. from theexchange-end transmission/reception device LTU.

[0071] During a time period t_(ECL), a signal W_(ECL) is transmitted,which means that echo cancelation is performed from the exchange end.Steps S107-S108 corresponding [sic] to the sequence of a conventionalmethod for transmitting data streams which has been described withreference to FIG. 3. Following step S107, the subscriber-endtransmission/reception device is in an operating state, which means thata subsequent subscriber-end acknowledgement step S109 is effected usinga signal W_(OKN).

[0072] The exchange end performs synchronization in a step S108, with asignal W_(SL) being provided. At a time denoted by an arrow (b) in FIG.1, both the exchange-end transmission/reception device LTU and thesubscriber-end transmission/reception device NTU are in an operatingstate.

[0073] A further, exchange-end acknowledgement step S110 is followed byordinary data transmission, with both transmission/reception devicesbeing transparent to user data, referred to as data stream transmissionstep Sill in the exemplary embodiment shown in FIG. 1.

[0074]FIG. 2 shows a flowchart for an exemplary embodiment of theinventive method for transmitting data streams, where a start step S100is followed by a subscriber-end activation step S101, and this isfollowed by an exchange-end activation step S102.

[0075] As explained above with reference to FIG. 1, steps S103 to S106comprise an exchange-end transmission line determination step S103, asubscriber-end transmission line determination step S104, asubscriber-end realignment step S105 and an exchange-end realignmentstep S106.

[0076] The dashed lines routed to the subscriber-end synchronizationstep S107 illustrate that it is possible to prescribe whether none or atleast one of the steps S103-S106 is to be performed, but any order canbe used.

[0077] Performance of none, one or a plurality of the inventive stepsS103-S106 is followed by a subscriber-end synchronization step S107, anexchange-end synchronization step S108 and a data stream transmissionstep S111, as in methods for transmitting data streams in accordancewith the prior art, for example described with reference to FIG. 3.

[0078] Data transmission is terminated with a stop step S112.

[0079] A considerable economic advantage of the present invention isthat a warm start sequence is of very flexible design, with itadditionally being possible to determine, in a cold start phase, controlby previously unused bits for the segments which are to be performed inthe warm start phase. In addition, it is possible to determine aselection of time periods for the segments in the cold start phase.

[0080] With regard to the flowchart shown in FIG. 3 for a conventionalmethod for transmitting data streams, reference is made to theintroduction to the description.

[0081] Although the present invention has been described above on thebasis of preferred exemplary embodiments, it is not limited thereto, butrather can be modified in a variety of ways.

1. Method for transmitting data streams where transmission/receptiondevices (LTU, NTU) deactivated to a standby state are activated byperforming a warm start sequence, with activation at a previous timehaving determined which of the following steps in the warm startsequence are performed: a) transmission line parameters are determined(S103) using an exchange-end transmission/reception device (LTU)following provision of a subscriber-end transmitted signal (S101); b)transmission line parameters are determined (S104) using asubscriber-end transmission/reception device (NTU) following provisionof an exchange-end transmitted signal (S102); c) echo cancelation isrealigned (S105) using a subscriber-end transmission/reception device(NTU) following provision of a subscriber-end transmitted signal (S101);and d) echo cancelation is realigned (S106) using an exchange-endtransmission/reception device (LTU) following provision of anexchange-end transmitted signal (S102).
 2. Method according to claim 1,characterized in that an activation frame respectively contains at leasttwo bits for each data transmission direction, said bits determiningwhich of the steps a) to d) are performed.
 3. Method according to one ormore of the preceding claims, characterized in that time periods forsignals used to realign echo cancelation are transmitted duringactivation at a previous time.
 4. Method according to one or more of thepreceding claims, characterized in that time periods for signals used todetermine the transmission line parameters are transmitted duringactivation at a previous time.
 5. Method according to one or more of thepreceding claims, characterized in that waiting time periods can beprescribed on a variable basis between successive sequences.
 6. Methodfor transmitting data streams where transmission/reception devices (LTU,NTU) deactivated to a standby state are activated by performing a warmstart sequence, having the following step: transmission line parametersare determined (S103) using an exchange-end transmission/receptiondevice (LTU) following provision of a subscriber-end transmitted signal(S101).
 7. Method for transmitting data streams wheretransmission/reception devices (LTU, NTU) deactivated to a standby stateare activated by performing a warm start sequence, having the followingstep: transmission line parameters are determined (S104) using asubscriber-end transmission/reception device (NTU) following provisionof an exchange-end transmitted signal (S102).
 8. Method for transmittingdata streams where transmission/reception devices (LTU, NTU) deactivatedto a standby state are activated by performing a warm start sequence,having the following step: echo cancelation is realigned (S105) using asubscriber-end transmission/reception device (NTU) following provisionof a subscriber-end transmitted signal (S101).
 9. Method fortransmitting data streams where transmission/reception devices (LTU,NTU) deactivated to a standby state are activated by performing a warmstart sequence, having the following step: echo cancelation is realigned(106) using an exchange-end transmission/reception device (LTU)following provision of an exchange-end transmitted signal (S102).